Burner



Sept. 21 A1926.

w. H. FvrrcH BURNER Filed' Nov. 22. 192s INVENTOR v TTORNEY PatentedSept. 21, v1926.

UNITED STATES `APATENT oFFlcE.

BURNER.

Application filed November 22, 1923. Serial No. 676,248.

This :invention relates to a burner for firing fuel in pulverized form,which is adapted for use in connection with furnaces generally, such asstationary boiler furnaces,

metallurgical furnaces, 'cement kilns, etc., although it has been ,foundof particular value as a burner for metallurgical furnaces in whichintensely high heat or, in other words, high CO2 is developed.

The burner is designed to produce a short flame of low velocity and highheat intensity and to prevent an accumulation of partly burned vfuel orcoke about the discharge orifice of the burner. Dificulty with cokingabout the discharge orifice is a common fault with the present type ofburners in use for firing pulverized fuel, the coke forming about theburner orifice and building up to an extent which results .eventually inthe restriction or virtual. closing up of the orifice. This necessitatescleaning out the v burner periodically which is a troublesome operationand furthermore, cannot be done without a temporary suspensionofoperation, Moreover,- pulverized fuel burners, as

heretofore designed, and used in practice,

provide'in themselves no means of regulating the velocity of the mixtureof pulverized fuel and air vwhichy they feed to the furnace; or if thisis arranged for at all, the means employed have been ineffectual toaccomplish the desired results. Generally speaking, such burners aredesigned to proyduce a combustible mixture of fuel and air by adding tothe-fuel and primary air, or carrier'air for conveying the fuel into thefurnace, a certain amount off-'secondary air to obtain better mixture.and'to furnishv additional air required for combustion. '.lhe secondary.airis usually brought'l into the burner mixing chamber by inductioncaused by the jet of `fuel and primary air. lIn

order thatth'e necessary amount of fuel may -be introduced to createthehigh heat required, as for example, in metallurgical furnaces,r themixture off,ue'l and air must 'be introduced into th'e furnace-athighQvelocity. v Such a jet produces along ain'e'fwith consequent widedistribution of heat 'oftlesser intensity and imping'ement of theflameon the opposite wall of the'furnace with resultant destruction' of therefractories.

The burner constituting the present invention comprises a chamber havingthe usual discharge orilicefrom which the mixture of fuel and airissues. Extending through the chamber, and iii-alignment with thedischarge orifice, is a feed pipe forconveying the mixture of fuel andprimary alrthrough the chamber for projection out of the dischargeorifice. The rimary air, it will be understood, is air un er pressure,or

an air blast, customarily sup lied by a fan,

and this air. serves to carry t e fuel in suspension through thefeedpipe in the burner.

erably in the form of a valve of approximately conical formation, whichis capable of being moved toward and away from the discharge orifice ofthe burner chamber.

The secondary air is constrained by the valve, and the walls' of thechamber surrounding the discharge orifice, t0 flow into the path of thejet of fuel and primary air, and it will be readily seen that where thissecondary air is under pressure a very thorough mixture of fuel and airis obtained in the burner before discharge from the outlet orificethereof. Furthermore, by adjustment of the valve toward and away fromthe discharge orifice, the velocity as well as the volume of thesecondary air entering the jet of fuel'and primary air is controlled inaccordance. with the velocity of the latter stream and the requirementsof combustion.

projected .at re atively high velocity the valve is adjustedv towarditslextreme open positionh so that greater quantities of secondary air areadded as combustion air, needed td consume the increased quantity offuel; bntvvhere a small quantity of fuel is beingconsumed, the valve is.adjusted toward the discharge orifice to obtain a ,corre/spondinglysmaller supply of secondary'fair' for combustion. 'Under eitherextreIneor intermediate conditions of operation,' the valve is adgustedin accordance with-the requirements. An important fea- .-ture ofoperation, however, is that the sec-v ondary air,jespeciallywhere underpressure, and directed against the fuel and primary air stream, as.described, cuts. down the ,ve-

locity thereof and the resultant fuel and air stream issuingfrom thedischarge orifice is considerably reduced in velocity. Thus projectedinto the furnace, the fuel mixed with air entering at aireduced velocityproduces a relatively short intensely hot flame with concentration orlocalization of heat and elimination of impingement on the walls of thefurnace. The direction of the secondary air againstthe issuing fuel jetmixed with primary air, furthermore, ensures thorough mixture of thefuel and air within the burner prior to its injection into the furnaceand also by virtue of its velocity and impingement against the innerwalls of the chamber, prevents lodging'and accumulation of fuel aroundthe burner opening and consequently the formation of coke. The form ofburner at present preferred is illustrated in the `accompanying drawing,wherein the burner is shown positioned in the wall of the furnace whichis simply indicated.

Referring to the drawing, the burner includes a casing 1 forming achamber provided with a discharge orifice 2 at one end thereof, and isshown positioned in theopening 3 of the furnace wall 4. In alignmentwith the orifice 2 and extending through the chamber 1 is a supply orfeed pipe 5 into which fuel and the primary or carrier air areintroduced, from sources not shown, but which arrangements are wellunderstood. The lower portion of the chamber 1 is provided with an-extension 6 which provides the connection to the source of thesecondary air supply, also not shown, but likewise well understood. The.primary air supply or carrier air for the fu'el introduced into the feedpipe 5 is usually supplied by a centrifugal fan and the'inlet 6 forsecondary air is also preferably connected to a source of air supplyunder ressure which may be a centrifugal fan. ounted on the feed pipe 5is a valve 7 having an integral sleeve portion 8 which fits over thefeed pipe 5 and is adapted to slide thereon. The lower part of thesleeve portion 8 is formed with rack'teeth 9 which are adapted to beengaged by a pinion 10 mounted on a shaft 11. The shaft 11 is supported,in the walls of the casing or chamber 1 and at its outer end carries ahand wheel 12 by which the valve member is adjusted.

The head portion of the valve is of approximate conical formation and ishollow as at 13 primarily to reduce its weight.

The valve head forms the incoming secondary air in the chamber 1 in ahollow conical body which is constrained by the valve and the confiningwalls of the chamber 1 to intersect at an' angle the fuel and primary-air issuing from the feed pipev5. The valve is adjustable by the`mechanism provided, toward and -away from the outlet opening 2inaccordance with the requirements of combustion, and the space betweenthe face of the. valve and the walls of the chamber serves as a smallmixing chamber in 'which the secondary air flowing around the edges ofthe valve mingles with the fuel and air mixture passing outward throughthe opening in the valve. Owing to the angle at which the secondary vairintersects the stream offuel and primary air, a thorough mingling of theair and fuel is brought about in this mixing chamber, and the size 0fthe mixing chamber and the effectiveness of the mixing action can becontrolled by moving the valve and thus varying the angle at which thestreams intersect. It will be seen also that the secondary air passingaround the valve head 7 provides a constantly moving body of air incontact with the inside wall of the casing 1 about its outlet orifice 2,the velocity of this moving body of air depending upon the adjustment ofthe valve and the accumulation of fuel about the orifice withlconsequent colring is thus prevented. It has been found in practicethat the burner described in the foregoing will roduce a most excellentmixture of fuel and air and a 'short intenselyv hot Haine without cokingdifficulties as before noted, and the CO2 obtainable has been in theneighborhood of 151/2 to 16%.

l claim 1. A burner for pulverized fuel comprising a casing having anoutlet opening in one wall thereof, a feed pipe for delivering a mixtureof pulverized fuel and air, this pipe terminating in the casing inalignment with the opening and at a distance therefrom, a valve membermounted on the pipe within-the casing and adjustable toward and awayfrom4 the opening, this valve member having a diameter greater than thatof the outlet opening in .the casing wall, and having a passage formedthroughA it of substantially the same diameter as that of the feed pipe,the fuel and air mixture discharging from the feed pipe and passingthrough this passage to flow through the outlet opening of the casing,and means for introducing yinto the casing an additional supply of airwhich mingles with the fuel 1 and air mixture passing out of the valvemember between the face of the latter and the outlet opening of thecasing.

2. A burner for pulverized fuel comprising a casing having an outletopening in one wall thereof, a Afeed pipe for delivering a mixture ofpulverized fuel and air, this pipe terminating in the casing inalignment with the opening and at a distance therefrom, a valve membermounted on the pipe within the casing and adjustable toward and awayfrom the opening, this valve member having a diameter greater than thatof the outlet opening in the casing wall, and having a passage formedthrough it of substantially the same diameter as that ofthe `feed pipe,the fuel therefrom,

-diameter than the outlet opening mount- I means for introducing anadditional supply ing, and means forintroducing an additional supply ofair to the casing vat a point behind the valve member, the air sosupplied being deflected outwardly toward the walls of the casing by thevalve member and flowing past the latter in the form of an an.- nularstream which joins the stream ofthe fuel and air mixture between the-valve member and the outlet opening. v

3. A burnerv for pulverized fuel comprising a casing having an outletopening in one wall thereof, a feed pipe fordelivering a mixture ofpulverized fuel and air, this pipe terminating in the casing inalignment with the opening and at a distance a valve member of larger edon the end of the pipe within the casing and with the walls of thecasing defining a mixing chamber between it and the outlet chamber, thisvalve member having a passage through it of substantially the samediameter as the feed pipe` through which the fuel and vair mixture fromthe feed pipe is discharged linto the mixing chamber and means for.,admitting an addi-y v tional supply of air into the casing at a'pointsuch that this additional air iows around the valve member and into thesaid mixing chamber, mingling with the stream of fuel and airissuing'from the valve member and passing with. that stream out of theoutlet opening. l

4. A burner for pulverized fuel comprise"v adjustment toward-and awayfrom the outlet opening to vary the size of this mixing chamber, andhaving a passage through it of substantially the same diameter as thefeed pipe through which the mixture -of fuel and air issuing from thefeed pipe is discharged into this mixing chamber, and

of air into the casing at apoi'nt such that the additional air flowsaround the valve memberand into the mi-xingchamber, where it mingleswith the fuel and air mixture and with thel latter'passes out throughthe 4'outlet opening. A

5. A burner for pulveri'zed fuel comprising acasing having an outletopening in one I end wa1l thereof, a feed pipe projecting' 'through theother end walland `terminating within the casing, this feed pipe beingin alignment.v with the outlet o ening aidadapted'v to deliver a`mixture o pulverized fuel andr air, means forV introducing an additionalsupply of air into the casing, and a valve member interposed betweentheoutlet opening and the point at `which this addiftional supply .of airis introduced, this vali e .member havingl a greater diameter than thaoutlet opening and having a passagethere through of substantially thesame4 size as th\v .feedvpipe, the fuel and lair mixture vissuing from.the feed. pipe owing through this passage and being discharged from'thelatter into thev casing, in alignment with theoutlet opening.

6. A burnerv for pulverized fuel comprisi ing a casing having an outletopening in one end wall thereof, a feed pipe projecting through theother end wall and terminating within the casing, this feed pipe beingin alignment with the outlet o ening and adapted to deliver a mixture opulverized lfuel and air, means for introducing an additional supply ofair into the casing, a valve memberinterposed between the outlet openingand the point at which this additional supply of air is introduced, thisvalve member having a greater diameter than the outlet yopening andhaving a passage therethrough) of substantially the same size as thefeed pipe, the fuel and air mixture issuing from the feed pipe flowingthrough this passage and being discharged from the latter into thecasing in alignment withthe outlet opening, and means-for adjusting thevalve member toward and away from the outlet opening. Y

7. A burner for pulverized fuel comprising a casing having a dischargeopening, a feed pipe extending into the casing in alignment with theopening and terminating at a distance therefrom, this pipe being adaptedto deliver a mixture of pulverized fuel and primary air, a cone-shapedvalve member within the casing having a fiat base lying in opposition tothe opening, the base being of greater diameter than the opening, andthis valve member having a. passage through it of substantially the samediameter as the feed pipe through which the mixture of pulverized fueland air issuing from the feed pipe flows in itspassage to the dischargeopening, and means for admitting a supply of additional air into thecasing at a point to the rear of the valve member, the additional airflowing along the inclined surfaces of the latter and around the edge ofthe base in the form ofan' annular stream surrounding the stream ofpulverized fuel vand air, the two streams mingling between ing fa casinghaving a discharge opening, a feed pipe extending into the casing inalignment with the opening and terminating ata distance therefrom, thispipe being adapted to deliver a mixture of pulverized fuel and primaryair, a Cone-shaped valve member lwithin the casing having a fiat baselying in opposition to the opening, the baseA from the feed pipe flowsin its passage to the discharge opening, means for admitting a supply ofadditional air into the casing at a-point to the rear of the Valvemember, the additional air flowing along the inclined surfaces ofthelatter and around the edge of the base in the form of an annular streamsurrounding the stream of pulverize'd fuel and air, the two streamsmingling between the base of the valve member and the outlet opening,and means for adjusting the Valve member toward and away from theopening.

In testimony whereof I aiiX my signature.

WILLIAM HENRY FITCH.

